The notion of class of graphs with bounded expansion was introduced by Nešetřil and Ossona de Mendez in [1]}. Its precise
definition can be found in Section REF . At this point it is only useful
to know that it contains the class of graphs of bounded degree, the class of
graphs of bounded treewidth, the class of planar graphs, and any class of graphs
excluding at least one minor. This notion is generalized to classes of structures
via their Gaifman graphs or adjacency graphs.
